Mechanically and electrically interlocked electromagnetic contactors



1967 w. L. DIETRICH ET AL 3,336,547

MECHANICALLY AND ELECTRICALLY INTERLOCKED ELECTROMAGNETIC CONTACTORS Filed Sept. 27, 1965 2 Sheets-$heet 1 F/ G 2 By Meir af/ameys Aug. 15, 1967 w. L. DIETRICH ET AL MECHANICALLY AND ELECTRICALLY INT 3,336,547 ERLOCKED ELECTROMAGNETIC CONTACTORS 2 Sheets-Sheet 2:

Filed Sept. 2'7, 1965 mm 0 5 5 LJ@ f @m w W? 0 a v e m W RMC United States Patent O MECHANICALLY AND ELECTRICALLY INTER- LOCKED ELECTROMAGNETIC CONTACTORS Walter L. Dietrich, Windsor, and Robert J. Petitjean,

Simsbury, Conn, assignors to The Arrow-Hart & Hegeman Electric Company, Hartford, Conn., a corporation of Connecticut Filed Sept. 27, 1965, Ser. No. 490,351 12 Claims. (Cl. 335-160) This invention relates to electromagnetically operated contactors and, more particularly, to interlocked electromagnetic contactors and means to positively and automatically cause the magnet to release and drop out should the magnet be held in because of loss of air gap, or sticky substance on the pole faces, or if the mechanism should not drop out for any reason.

Electromagnetic contactors used in pairs such as, for example, to encircuit a motor for forward or reverse running have frequently had to be connected together mechanically so that when one contactor is energized and its contacts are closed, the contacts of the other contactor may not close if that other contactor is energized.

After prolonged use or particularly hard use, the magnet of one contactor or the other may tend to stick together or delay in separation due to scarring, wearing, contamination or loss of air gap. If for any reason, one contactor or the other should not open when deenergized, it is necessary that the armature and field piece of the magnet should be separated forcibly and the contactor compelled to drop out so as to continue in operation the apparatus with which the interlocked contactors are encircuited and which they control. Moreover, it is desirable that the force applied to separate the parts of the magnet and cause dropping out of the mechanism should be applied promptly and automatically at the contactors.

Heretofore when two contactors have been used such as for forward or reverse operation of an electric motor, interlocking means such as a bar connecting the armatures or actuating mechanisms of the two contactors have been used to keep one contactor from operating to close its contacts when the other has been operated or closed. Such interlocked contactors were operable by forward or reverse push buttons which closed the circuits to the solenoid coils of the contactors.

If the coil of one contactor was deenergized and it failed to drop out because of stuck-together magnet parts or because of other reasons, the button controlling the other contactor could be pushed and it would apply a force to close its contactor and, because of the interlock, it would also incidentally apply a force tending to open the magnet of the contactor which had not dropped out. But such-action was not automatic. It would not function without human intervention. Moreover, the operator would only know something was amiss when he observed the motor continuing to run after he had pushed the stop button. Unfortunate consequences could occur due to this period of unexpected and unwanted continuance of operation.

Therefore, it is an object of this invention to provide means which operates automatically to cause interlocked electromagnetic contactors to drop out whenever they are deenergized, but delay or fail to drop out due to a frozen or stuck magnet or for other reasons.

Another object of the invention is to provide means to apply a force automatically to assist the springs which customarily bias electromagnetic contactors open, so that frozen or stuck magnets of the contactor may be separated automatically.

Another object is to utilize one contactor to apply a force automatically to cause the other of two interlocked 3,336,547 Patented Aug. 15, 1967 ice contactors to drop out whenever either fails to do so for any reason.

Other objects and advantages of the invention will be come apparent as it is described in connection with the accompaning drawings.

In the drawings:

FIG. 1 is a top plan view of a pair of interlocked elec tromagnetic contactors embodying the invention.

FIG. 2 is a front elevation view of the contactors and invention of FIG. 1.

FIG. 3 is an end elevation view, partly in section, of the invention as illustrated in FIGS. 1 and 2.

FIG. 4 is a fragmentary detail view, partly in section, of the fulcrum bracket as associated with the interlocking bar and base plate.

FIG. 5 is a wiring diagram illustrating the connections between the contactors and the power lines and the various auxiliary precision switches and overload devices which are used in connection with the invention.

Referring to the drawings, two electromagnetic contactors of the type disclosed in the Harold E. Schleicher Patent 2,719,890 issued Oct. 24, 1954 are mounted upon a sheet metal base plate 10. These electromagnetic contactors are identical and, hence, only the structure of one will be described. For details of construction of such contactors, reference may be had to said patent. However, the invention is not limited to the electromagnetic contactors so constructed, but is applicable to electromagnetic contactors generally.

As illustrated, each contactor has a one-piece stamped sheet metal frame of generally U-shape with its transverse portion 12 secured to the base plate 10 and its side plates 14, 16 perpendicular to the base plate with their top edges inwardly bent forming flanges 14 16]. On these flanges, an insulating member 18 is mounted which carries sets of fixed contacts 21, 23 which are bridged by movable contact members 25. There may be as many sets of contacts and bridging members as desired or needed in particular usages. The bridging contacts 25 are insulatedly supported upon a movable yoke of inverted U-shape having parallel side arms, such as 27.

Each side arm is pivotally connected by a pin such as 29 to a triangular bell-crank member such as 40. These members are pivotally mounted on the side plates 14, 16 of the frame by fixed studs such as 42.

The bell-crank members are moved by driving links such as 36 which are pivotally connected to the bell-crank members by pins such as 41 and move parallel to the base plate 10.

The inner ends 38, 38' of the drive links are bent at a right angle toward the side plates of the frame, each affording an anchor for a biasing spring 69 and a mounting for an adjustment screw 37 whose functions and purposes are hereinafter described.

The driving links are driven by a conventional T- shaped movable armature 50 of an electromagnet having a conventional C-shaped field piece 52 in which is mounted the solenoid coil 54. The armature is drawn into the solenoid when the solenoid is energized in usual and conventional fashion.

The armature 50 is connected to the driving links 36 by transverse drive rod 56 whose ends pass freely through the ends of the driving links. The extremities of said driving rod extend through and are guided for sliding movement parallel to the base plate 10 by identical slots in each of the side plates 14 and 16 of the frame. To connect the armature to the drive rod 56, a U-shaped metal strip 58 has its ends attached to the armature and is looped around the drive rod at its midpoint.

When the solenoid 54 is energized, the armature is attracted and moves into face of the field piece 52.

50 the solenoid and engages the This moves the drive rod 56 parallel to the base plate and pushes the driving links 36 and, by their pivotal connection 41, also pushes the bellcrank members, causing them to turn about their fixed pivots 42. Thereupon, the pin connection 29 of the bellcrank members with the arms 27 of the contact operating yoke moves that yoke and moves the bridging contacts 25 into engagement with the fixed contacts 21 and 23.

During the foregoing, the lower end of the side arms 27 is guided by a pivotal connection to the side arms 62 of a stamped sheet metal U-shaped guide member. This member has a transverse portion 64 connecting its parallel side arms 62 and is pivotally mounted in the side plates 14 and 16 of the frame by pivot pins 66 passing through the side arms adjacent their connection to the transverse portion. The ends of the arms are pivotally connected by pin such as 68 to the lower ends of the side arms 27 of the contact operating yoke.

A pair of springs 69, connected to the pivot pins 66 at one end and at their other ends connected to the driving links 36, biases the operating mechanism just described toward an inactive position. This is the position which the parts occupy when the solenoid is not energized. In this inactive or dropped-out position, the contacts are disengaged or open.

In order to prevent operation of one contactor when the other is energized and its contacts are closed, an interlocking bar 70 is connected between the armatures of the forward electromagnetic contactor FMC and the reverse electromagnetic contactor RMC (see FIGS. 1 and 2). The bar 70 is formed as a strip of stamped sheet metal whose ends are twisted in the same direction into the same plane at right angles to the plane of the central portion of the bar. Each end of the bar is loosely attached by rivets 71 to identical parallel tabs 72, 72 which extend from the transverse portion of U-shaped brackets 74. A bracket is provided for each contactor and each is mounted upon the driving rod 56 of its own contactor by passage of the driving rod through apertures in the arms of the brackets. The two tabs 72, 72' extend through slots in the midportion of each bracket 74 and these tabs lie against the opposite faces of their end of the interlocking bar. The rivets 71 pass through the tabs and through the ends of the bar loosely, whereby the ends of the bar are secured pivotally to the tabs. So that the tabs will not fall out of the slots in which they are lodged, they have enlarged heads inwardly of the transverse portion of the bracket.

A fulcrum about which the interlocking bar pivots at its midpoint is afforded by an adjustment screw 76 having a pointed end. To support the screw 76 parallel to the base plate and perpendicular to the interlocking bar, a fulcrum bracket 80 in the form of a bent strip of sheet metal is provided (see FIG. 4). It has an obliquely angled central portion, one end of which is bent to be flat on the base plate and be secured thereto by a screw 81 while the other end lies on top of a post 82 between itself and the base plate 10. The post and fulcrum bracket 80 are secured to the base plate by a bolt 83 passing through the post and threading into a tapped hole in the base plate. The extremity 81 of such other end of the bracket is turned upwardly prependicular to the base plate and has a tapped hole for the adjustable fulcrum screw 76. To hold the interlocking bar 70 in proper position over the base plate and in position to pivot against the end of the adjustment screw 76 and also to loosely guide the pivotal movement of the interlocking bar, a U-shaped stamped sheet metal guide bracket 85 is mounted on the upturned extremity 84 of the fulcrum bracket 80. The transverse portion of this bracket lies against said upturned extremity while the parallel arms of the bracket lie above and below the edges of the interlocking bar.

From the foregoing, it will thus be seen that as the solenoid of the contactor FMC is energized, its armature will be attracted and will pivot the interlocking bar 70 A precision switch unit PF is attached to the outer I side plate of the frame of the forward contactor FMC by means of a flat mounting plate 87 which at one end is attached by screws to the side plate of the frame while its other end is similarly attached to the casing of the precision switch.

Another precision switch PR is similarly afiixed to the outer side plate of the frame of the other contactor RMC. Such precision switches are available on the market and are characterized by mechanism which has ability to utilize a slight movement (such as .010 inch) of an operating plunger member or button 88 in one direction or the other to cause a movable contact to engage or disengage a fixed contact (not shown) with a snap action. The precision switches used here are of the biased normally-open contact type of single-pole switch.

Each precision switch has an operating button or plunger 88 extending from the switch casing 89 and located in position for the end of the adjustment screw 37 on the bent arm 38 of the driving link 36 to engage the plunger 88 as the driving link nears the end of its travel when the solenoid of the electromagnet is energized for closing the power contacts of the contactor. At such time, the power contacts of the contactor will have become engaged and the usual contact back-up springs (not shown) behind such power contacts are being compressed. Such small increment of motion (lost motion) as the back-up springs are compressed is adequate to operate a precision switch and cause closing of the precision switch contacts.

To provide fine adjustment of the time of opening and closing of the contacts of the precision switches, the adjustment screw 37 on the bent arm 38 is manipulated.

As will become apparent in connection with the description of the circuit, an auxiliary switch AF or AR is necessary in connection with each contactor. Each auxiliary switch is mounted on the side plate of the frame of its contactor by screws or by any suitable means. Such switches are conventional types of button-actuated singlepole switches available on the market. Each comprises a casing 90 housing a pair of contacts (not shown) biased normally-closed and operable by a plunger or button 92 which extends from the switch casing in position to be operated by the bent arm 38 of the driving link of the contactor. This driving link is on the opposite side of the contactor from the driving link which operates the precision switch.

From the foregoing, it can be understood that on energization of the solenoid of the contactor FMC, its mechanism will cause closing of the power contacts 21, 25, 23 and simultaneous opening of the contacts of the auxiliary switch AF; and then during the final portion of the travel of this contactor mechanism, the contacts of the precision switch PF will close.

Likewise, when the solenoid of the RMC contactor is energized, the mechanism of RMC will close its power contacts and simultaneously open the normally-closed contacts of the auxiliary switch AR. Then at the final portion of the travel of the contactor mechanism, the contacts of the precision switch PR will close.

The inter-locking bar will prevent the operating mechanism of both contactors from moving to switch-closed" position, at the same time.

In order to control the energization of the contactors, two similar control switches are provided. These control switches are or may be located at a point remote from the contactors and are shown only diagrammatically as CF and CR in FIG. 5. The control switches may be conventional switches having two active positions wherein a movable contact connects one switch terminal with one or the other, alternatively, of two fixed switch contacts and their terminals, as shown in the control switches AF and AR in FIG. 5.

Referring to the diagram of FIG. 5 and assuming that the contactors are both deenergized and have dropped out, the control switch CF may be moved to the dotted position for the purpose of operating the forward electromagnetic contactor FMC. Thereupon, current will flow from L through contacts a and c of control switch CF and through the contacts of the normally-closed auxiliary switch AR mounted on the reversing contactor RMC. The current then flows through solenoid coil Fs of forward contactor FMC to line L It will be recalled that the AR contacts, although in the circuit of'the forward contactor solenoid coil Fs, are controlled by the position of the mechanism of the reversing contactor RMS.

When the control switch CF is moved to the full-line position for the purpose of deenergizing the forward contactor and causing it to drop out, the circuit to the forward solenoid coil Fs will be open between contact a and 0. However, if the forward contactor fails to drop out for any reason, then the contacts of the precision switch PF will remain closed. As a result, the current from L can flow through contacts a and b of control switch CF, then through the contacts of precision switch PF to the solenoid Rs of the reversing contactor RMC to line L The energization of coil Rs causes the mechanism of the reversing contactor RMC through the action of interlocking bar 70 to impose a force on the mechanism of the forward contactor in a direction to cause the forward contactor to drop out. This force added to the biasing action of the springs of the forward contactor overcomes the sticking action of the magnet (or other condition which has been holding the contactor closed) and forces the contactor to drop out. During the first fraction of its dropping-out action, the contacts of precision switch PF open, breaking the circuit to solenoid Rs so that RMC then drops out. The parts are so proportioned and the fulcrum screw 76 is so adjusted that the force which is exerted by the reversing contactor mechanism and which acts to cause the forward contactor to drop out is exerted immediately, before the power contacts of the reversing contactor can engage. Thus, the forward contactor is dropping out before the reversing contactor contacts close. If the power contacts of contactor RMS close at all, such closing will be only momentary and of no consequence because the reverse contactor does not remain energized and will immediately drop out again.

The operation of control switch CR is similar to that of control switch CF. The double-dotted position of the CR switch causes energization of solenoid coil Rs and closing of the RMS. Alternatively, movement of CR to the full-line position will normally cause the contactor RMC to drop out. But if contactor RMC does not drop out then, forward contactor coil Fs will be energized and its force will be exerted through the FMC operating mechanism to force RMC to drop out.

In describing the invention in connection with FIG. 5, it has been assumed that two separate control switches PF and PR are used.

It is also possible to use only one control switch capable of occupying three active positions. In such case, a movable switch contact will connect one switch terminal with any one of three stationary switch contacts. In such a case, the contacts b and d of the diagram of FIG. 5 would be combined and would be an intermediate switch contact to which connections are shown for contacts b and d would be made.

The operation of the control switches CF and CR is selective. If one (such as CF) is moved to energize the solenoid it controls (such as Fs), the movement of the mechanism of that contactor (such as FMC) to actuated position will open the circuit to the solenoid of the other contactor (such as RMC) at the contacts of the auxiliary switch (such as AF). Hence, movement of the control switch for the other contactor (such as CR) to energize its solenoid (such as Rs) will be ineffective. The first contactor (such as FMC) must first drop out before the second can be actuated under manual control. But, automatic operation of the second contactor will take place as above described.

It is desirable, therefore, for the auxiliary switches to adjusted so as to open and close at the same time as the power contacts of the contactors close and open.

Although two interlocked switches have been shown and described, the invention could be applied to three or more so that adjacent contactors could be energized to cause release of stuck contacts or mechanisms.

Many modifications will occur to those skilled in the art. Therefore, the invention is not limited to the specific embodiment illustrated and described.

What is claimed is:

1. In combination, a plurality of electromagnetically operable contactors, means interconnecting said contactors and preventing operation of more than one at a time, switch means controlling actuation and deactuation of said contactors selectively, and means to cause actuation of a second contactor automatically on deactuation of a first contactor if the latter fails to drop out, the actuation of said second contactor applying a force tending to cause said first contactor to drop out.

2. The combination as claimed in claim 1 in which the force of said second contactor incident to its automatic actuation is applied through said interconnecting means to said first contactor.

3. The combination as claimed in claim 2, and means to automatically deactuate said second contactor as said first contactor drops out.

4. The combination as claimed in claim 1, and means to maintain the automatic actuation of said second contactor until said first contactor drops out and then to deactuate said second contactor.

5. The combination as claimed in claim 1 wherein the interconnecting means includes a pivoted bar connected to adjacent contactors whereby actuation of one contactor moves said bar into a position wherein movement of the other to actuated position is opposed.

6. The combination as claimed in claim 5 having an adjustable fulcrum point for said bar between said contactors.

7. The combination as claimed in claim 1 in which the control switch means comprises switching means movable into two conducting positions, and in which the means to cause automatic actuation comprises switching means moved into and maintained in closed-circuit condition by said second contactor while the latter remains in actuated position.

8. The combination as claimed in claim 7, and normally-closed switching means movable into and maintained in open circuit position by said second contactor when the latter is actuated and preventing said control switch means from actuating said first contactor while said second contactor is actuated.

9. The combination as claimed in claim 8 wherein said means to cause automatic actuation comprises a precision switch having an actuator and switch contacts, said actuator being operated to close said switch contacts during the final portion of the actuation of the contactor with which said precision switch is connected and to reopen said contacts on return movement of said contactor.

10. The combination as claimed in claim 1 wherein said means to cause automatic actuation comprises a precision switch having an actuator and switch contacts, said actuator being operated to close said switch contacts during the final portion of the actuation of the contactor with which said precision switch is connected and to reopen said contacts on return movement of said contactor.

11. The combination as claimed in claim 1 in which the control switch means comprises switching means movable into two conducting positions in one of which said first contactor is actuated, said control switch means in its other position causing actuation of said second contactor if said first contactor does not drop out.

12. The combination as claimed in claim 1.in which the control switch means comprises switching means movable into two conducting positions in one of which said first contactor is actuated, said control switch means in References Cited UNITED STATES PATENTS 8/1948 Nelsen 335-460 X 4/1959 Mckelburg 335--l60 BERNARD A. GILHEANY, Primary Examiner.

R. N. ENVALL, JR., Assistant Examiner. 

1. IN COMBINATION, A PLURALITY OF ELECTROMAGNETICALLY OPERABLE CONTACTORS, MEANS INTERCONNECTING SAID CONTACTORS AND PREVENTING OPERATION OF MORE THAN ONE AT A TIME, SWITCH MEANS CONTROLLING ACTUATION AND DEACTUATION OF SAID CONTACTORS SELECTIVELY, AND MEANS TO CAUSE ACTUATION OF A SECOND CONTACTOR AUTOMATICALLY ON DEACTUATION OF A FIRST CONTACTOR IF THE LATTER FAILS TO DROP OUT, THE ACTUATION OF SAID SECOND CONTACTOR APPLYING A FORCE TENDING TO CAUSE SAID FIRST CONTACTOR TO DROP OUT. 